Joao Rocha

Despite the growing need for advanced monitoring solutions to support infrastructure maintenance, driven by the ongoing expansion of the transportation network, and the structural importance of unbound granular layers in flexible pavements, their continuous monitoring remains subject to significant technical challenges. This article describes the development of a system for monitoring the dynamic stiffness of these layers using Bender Elements sensors. A protection and coupling system was designed to protect the sensors from external stresses and ensure proper contact with the geomaterial to propagate the shear wave through it. The design was optimized through numerical analysis of the capsule’s geometry and laboratory tests to improve the selection of components for the coupling system. The system was subsequently validated in a large compaction box using unbound ground material extracted from the field as the medium between the sensors, to determine the optimal sensor spacing distance for installation to ensure detection of a high-quality signal. Following this, the complete design of the monitoring system was developed and implemented in the field. Finally, the signals obtained under real conditions were processed, with measures considered to eliminate persistent interference and crosstalk. Thus, it was confirmed that the monitoring system performed well as a tool for continuous monitoring of dynamic stiffness and was suitable for the practical requirements of structural evaluation of unbound ground material layers.

This article presents the design and implementation of a DC–DC power converter for application in electric vehicle (EV) fast-charging systems. The prototype is of the resonant LLC type and consists of a high-power transformer operating at high frequency, which is an essential feature for the adequate behavior of the EV fast-charging system as a whole. As demonstrated throughout the article, by using this converter topology as well as its specific operating modes, such as for achieving zero-voltage switching (ZVS) and zero-current switching (ZCS), it is possible to enhance efficiency by reducing conduction and switching losses as well as to increase power density. The details of the high-power high-frequency transformer (HFT), considering different designs, are presented and discussed. With the implemented laboratorial prototype fully developed with silicon carbide (SiC) power semiconductor devices, it was possible to demonstrate and validate the main features of the resonant LLC converter, including high efficiency, under distinct conditions of operation.